Serial Raw Socket IP transportation inputs characters from the incoming serial bit stream of a serial port and packetizes them into packets to be sent over an IP network. Importantly, only character data is packetized and transferred. This has the advantage of using a minimal amount of network bandwidth when compared to the more traditional way of carrying serial data over a C-Pipe, which transfers the entire bit stream including idle data. Both Serial Raw Socket IP transportation and C-Pipes are used in Supervisory Control and Data Acquisition (“SCADA”) applications.
The problem arises when the serial device connected to serial port starts “babbling,” which means to send a continuous stream of bad character data. When a serial port begins to send a continuous stream of bad character data, the adverse effect of “jamming” occurs on the listening device at the other end of the network which may prevent the listening device from communicating with other devices in the network.
There is currently no known solution for suppressing the ingress traffic of a serial port, at the serial port itself. The previous solution required the serial bit stream to be framed and the squelching/unsquelching was performed on the frame, which is not useable in a raw socket implementation where TDM (“Time Division Multiplexing”) frames are not used.
For example, there is an existing squelch and unsquelch solution implemented for serial data carried over a Multidrop Data Bridge (“MDDB”). However, the squelch and unsquelch feature is at the far-end of a typical C-Pipe. At this point in the serial data flow, the serial data has already been encapsulated into a framing format (for example, to carry sub-64 kbps traffic on a 64 kbps channel). Therefore, this squelching and unsquelching function is not usable in a Serial Raw Socket IP Transportation implementation because it requires framed data.